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Physical System (physical + system)
Selected AbstractsNaive Analysis of Food Web Dynamics: A Study of Causal Judgment About Complex Physical SystemsCOGNITIVE SCIENCE - A MULTIDISCIPLINARY JOURNAL, Issue 4 2000Peter A. White When people make judgments about the effects of a perturbation on populations of species in a food web, their judgments exhibit the dissipation effect: a tendency to judge that effects of the perturbation weaken or dissipate as they spread out through the food web from the locus of the perturbation. In the present research evidence for two more phenomena is reported. Terminal locations are points in the food web with just a single connection to the rest of the web. Judged changes tended to be higher for species at terminal locations than for species the same distance from the perturbation but at nonterminal locations. Branches are points in the web where a route splits into two or more routes. Judged changes tended to be lower for species following branching points than for species the same distance from the perturbation but not following branching points. It is proposed that the findings can be explained as effects of a mental model employing concepts of influence and resistance. Under this model a perturbation is a change in energy level at a point in the system that acts as an influence affecting the rest of the system. The basic concepts in this model are domain-general and on that basis it is predicted that the dissipation effect should be found in judgments of any physical system to which notions of influence and resistance can be applied. [source] Application of the anharmonic coherent states to the vibronic interactionFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 2-3 2003C.N. Avram We calculated the vibronic reduction factor (Ham factor) for the physical system (molecules, crystals) with octahedral symmetry. The vibrations of the nuclei of the systems are described by the anharmonic states of the Morse potential and also by the anharmonic coherent states of the same potential. The linear vibronic coupling of these vibration states with the electronic states of the system are considered. [source] Non-equilibrium behaviour of equilibrium reservoirs in molecular simulationsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 12 2005Martin W. Tysanner Abstract We explore two widely used algorithms for fluid reservoirs in molecular simulations and demonstrate that they may induce non-physical non-equilibrium effects, even in systems that should be at equilibrium. For example, correlations of momentum and density fluctuations lead to a bias in the mean fluid velocity when measured as the mean over samples of instantaneous fluid velocity. The non-physical behaviour is entirely computational in origin and is an instance of a more general issue in molecular simulations: a failure to correctly model stochastic properties may induce non-equilibrium behaviour that does not exist in the corresponding physical system. Finally, we demonstrate that simple algorithm corrections eliminate this artifact. Copyright © 2005 John Wiley & Sons, Ltd. [source] Material Flows in a Social Context: A Vietnamese Case Study Combining the Materials Flow Analysis and Action-in-Context FrameworksJOURNAL OF INDUSTRIAL ECOLOGY, Issue 1 2007Marieke HOBBES Summary Materials flow analysis (MFA) is one of the central achievements of industrial ecology. One direction in which one can move MFA beyond mere accounting is by putting the material flows in their social context. This "socially extended MFA" may be carried out at various levels of aggregation. In this article, specific material flows will be linked to concrete actors and mechanisms that cause these flows,using the action-in-context (AiC) framework, which contains, inter alia, both proximate and indirect actors and factors. The case study site is of Tat hamlet in Vietnam, set in a landscape of paddy fields on valley floors surrounded by steep, previously forested slopes. Out of the aggregate MFA of Tat, the study focuses on material flows associated with basic needs and sustainability. The most important actors causing these material flows are farming households, politicians, traders, and agribusiness firms,of which local politicians turned out to be pivotal. The study shows the value of combining MFA with actor-based social analysis. MFA achieves the balanced quantification of the physical system, thus helping to pinpoint key processes. Actor-based analysis adds the causal understanding of what drives these key processes, leading to improved scenarios of the future and the effective identification of target groups and instruments for policy making. [source] Elementary Propositions and Essentially Incomplete Knowledge: A Framework for the Interpretation of Quantum MechanicsNOUS, Issue 1 2004William Demopoulos A central problem in the interpretation of non-relativistic quantum mechanics is to relate the conceptual structure of the theory to the classical idea of the state of a physical system. This paper approaches the problem by presenting an analysis of the notion of an elementary physical proposition. The notion is shown to be realized in standard formulations of the theory and to illuminate the significance of proofs of the impossibility of hidden variable extensions. In the interpretation of quantum mechanics that emerges from this analysis, the philosophically distinctive features of the theory derive from the fact that it seeks to represent a reality of which complete knowledge is essentially unattainable. [source] Stretching a plane surface in a viscoelastic fluid with prescribed skin frictionNUMERICAL METHODS FOR PARTIAL DIFFERENTIAL EQUATIONS, Issue 6 2009M. Sajid Abstract A model of forced convection flow due to stretching surface is derived to represent the physical system with prescribed skin friction. To achieve the similar solutions, the partial differential equations are reduced into ordinary differential equations. The analytic solutions of the resulting problems have been obtained by a homotopy analysis method. The convergence of the developed series solution is seen. Finally, the results of velocity, temperature, the stretching velocity, and Nusselt number are analyzed. © 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2009 [source] The dynamic behaviour of stacked shipping units during transport.PACKAGING TECHNOLOGY AND SCIENCE, Issue 5 2004Part 1: model validation Abstract This paper deals with the dynamic behaviour of stacked packaging units when subjected to vertical vibrational inputs as experienced in transport vehicles. Although the vibrational performance of single-unit packaging systems has been thoroughly studied, the behaviour of stacked packaging units is not fully understood. The complexity of the problem is compounded when the effects of vertical restraints are taken into account. The paper presents the development of a numerical computer model designed to predict the dynamic response of stacked package systems when subjected to vertical vibrational excitation. Provisions have been made to account for the effects of vertical restraint tension and stiffness. In addition, a physical model representative of a generic stacked packaging system has been developed to assist in validating the numerical model. The paper includes results from preliminary experiments in which the frequency response functions of the models were evaluated and compared. The validity of the numerical model in the time domain was tested using random burst excitation signals. These preliminary experiments reveal that, when the effects of frictional damping are taken into account, the numerical model can be used to generate reasonably accurate predications of the dynamic behaviour of the equivalent physical system. Copyright © 2004 John Wiley & Sons, Ltd. [source] The effective-site percolation approach in two dimensionsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2007G. Paw, owski Abstract A new Monte Carlo cluster approach to describe the order,order and order,disorder transitions in two-dimensional (2D) correlated systems is presented. It is shown that a phase transition of a physical system can be correctly described in terms of the percolation language of the effective-site approach. In contrast to the well-known bond approaches, the method proposed does not require additional assumptions as to the acceptance of the bonds. The new idea is based on the site approach to elementary ordered plaquettes, leading to the accurate coincidence of percolation and the phase transitions in 2D. Here I present the analysis of the spin-system in the Blume,Capel model and the charged-system in the atomic limit of the extended Hubbard model. In both cases the interpretation of the phase transition is made in terms of the percolation of different types of order. The new method allows precise identification of the pure and mixed phases. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Naive Analysis of Food Web Dynamics: A Study of Causal Judgment About Complex Physical SystemsCOGNITIVE SCIENCE - A MULTIDISCIPLINARY JOURNAL, Issue 4 2000Peter A. White When people make judgments about the effects of a perturbation on populations of species in a food web, their judgments exhibit the dissipation effect: a tendency to judge that effects of the perturbation weaken or dissipate as they spread out through the food web from the locus of the perturbation. In the present research evidence for two more phenomena is reported. Terminal locations are points in the food web with just a single connection to the rest of the web. Judged changes tended to be higher for species at terminal locations than for species the same distance from the perturbation but at nonterminal locations. Branches are points in the web where a route splits into two or more routes. Judged changes tended to be lower for species following branching points than for species the same distance from the perturbation but not following branching points. It is proposed that the findings can be explained as effects of a mental model employing concepts of influence and resistance. Under this model a perturbation is a change in energy level at a point in the system that acts as an influence affecting the rest of the system. The basic concepts in this model are domain-general and on that basis it is predicted that the dissipation effect should be found in judgments of any physical system to which notions of influence and resistance can be applied. [source] Self-Assembled Heteroepitaxial Oxide Nanocomposite Thin Film Structures: Designing Interface-Induced Functionality in Electronic MaterialsADVANCED FUNCTIONAL MATERIALS, Issue 13 2010Judith L. MacManus-Driscoll Abstract Achieving self-assembling/self-organizing systems is the holy grail of nanotechnology. Spontaneous organization is not unique to the physical sciences since nature has been producing such systems for millions of years. In biological systems global patterns emerge from numerous interactions among lower-level components of the system. The same is true for physical systems. In this review, the self-assembly mechanisms of oxide nanocomposite films, as well as the advantageous functionalities that arise from such ordered structures, are explored. [source] Disordered lattice networks: general theory and simulationsINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 6 2005Stefano GiordanoArticle first published online: 16 NOV 200 Abstract In this work we develop a theory for describing random networks of resistors of the most general topology. This approach generalizes and unifies several statistical theories available in literature. We consider an n-dimensional anisotropic random lattice where each node of the network is connected to a reference node through a given random resistor. This topology includes many structures of great interest both for theoretical and practical applications. For example, the one-dimensional systems correspond to random ladder networks, two-dimensional structures model films deposited on substrates and three-dimensional lattices describe random heterogeneous materials. Moreover, the theory is able to take into account the anisotropic percolation problem for two- and three-dimensional structures. The analytical results allow us to obtain the average behaviour of such networks, i.e. the electrical characterization of the corresponding physical systems. This effective medium theory is developed starting from the properties of the lattice Green's function of the network and from an ad hoc mean field procedure. An accurate analytical study of the related lattice Green's functions has been conducted obtaining many closed form results expressed in terms of elliptic integrals. All the theoretical results have been verified by means of numerical Monte-Carlo simulations obtaining a remarkably good agreement between numerical and theoretical values. Copyright © 2005 John Wiley & Sons, Ltd. [source] Students' use of the energy model to account for changes in physical systemsJOURNAL OF RESEARCH IN SCIENCE TEACHING, Issue 4 2008Nicos Papadouris Abstract The aim of this study is to explore the ways in which students, aged 11,14 years, account for certain changes in physical systems and the extent to which they draw on an energy model as a common framework for explaining changes observed in diverse systems. Data were combined from two sources: interviews with 20 individuals and an open-ended questionnaire that was administered to 240 students (121 upper elementary school students and 119 middle school students). We observed a wealth of approaches ranging from accounts of energy transfer and transformation to responses identifying specific objects or processes as the cause of changes. The findings also provide evidence that students do not seem to appreciate the transphenomenological and unifying nature of energy. Students' thinking was influenced by various conceptual difficulties that are compounded by traditional science teaching; for instance, students tended to confuse energy with force or electric current. In addition, the comparison between the responses from middle school students and those of elementary school students demonstrates that science teaching and maturation appeared to have a negligible influence on whether students had constructed a coherent energy model, which they could use consistently to account for changes in certain physical systems. © 2007 Wiley Periodicals, Inc. J Res Sci Teach 45: 444,469, 2008 [source] Seeing Through the Fog,Attaining ,Full Spectrum Dominance' with the System-of-Systems Through Operational EngineeringNAVAL ENGINEERS JOURNAL, Issue 4 2000R. E. Bryant ABSTRACT Many discussions and articles address the business and military changes supporting implementation of Joint Vision 2010 and its system-of-systems approach. The dynamics of international military operations and commitments, coupled with accelerating information technologies, can lead to confusion and uncertainty. Customary rules recommend caution, even stopping, when confusion and uncertainty are present, yet the needed changes counsel toward accelerated efforts. Currently, systems engineering does not completely address delivering "operational war fighting capabilities," or foster commanders' confidence to fully exploit those capabilities upon delivery. Acquisition reform supports accelerating delivery of systems. Likewise, accelerated delivery of "war fighting capabilities" within any opponents' fielding and deployment cycle is imperative. Technical advances in modeling and simulation, utilization concepts, and innovative evaluation methods create an opportunity to facilitate redevelopment of doctrine, operations, and training prior to producing hardware systems. On-line simulation and evaluation tools can overcome the need for physical systems. Specifically, this paper lays out the opportunity to evolve systems engineering to another level, operational engineering, which leverages from the modeling and simulation environment, prior to hardware production. That modeling and simulation paired with coevolution of procedures and on-line analysis will produce a trained customer base, fully prepared for deliveries of "operational war fighting capabilities". [source] From Universal Laws of Cognition to Specific Cognitive ModelsCOGNITIVE SCIENCE - A MULTIDISCIPLINARY JOURNAL, Issue 1 2008Nick Chater Abstract The remarkable successes of the physical sciences have been built on highly general quantitative laws, which serve as the basis for understanding an enormous variety of specific physical systems. How far is it possible to construct universal principles in the cognitive sciences, in terms of which specific aspects of perception, memory, or decision making might be modelled? Following Shepard (e.g., 1987), it is argued that some universal principles may be attainable in cognitive science. Here, 2 examples are proposed: the simplicity principle (which states that the cognitive system prefers patterns that provide simpler explanations of available data); and the scale-invariance principle, which states that many cognitive phenomena are independent of the scale of relevant underlying physical variables, such as time, space, luminance, or sound pressure. This article illustrates how principles may be combined to explain specific cognitive processes by using these principles to derive SIMPLE, a formal model of memory for serial order (Brown, Neath, & Chater, 2007), and briefly mentions some extensions to models of identification and categorization. This article also considers the scope and limitations of universal laws in cognitive science. [source] | |||||||||||||